This invention concerns an optical soil survey device to survey the optical characteristics of a given soil, a soil survey device to survey the soil, a soil survey system and a mobile soil survey vehicle to survey the soil. More specifically, it concerns the devices mentioned above which create, at a desired depth, a space in order to survey the characteristics of the soil.
This invention is used for precision agriculture, or farming for precision field management which is a relatively new agricultural concept.
In recent years the concept of precision field management has become increasingly popular as a means of preserving the environment and at the same time insuring a profit. The objective is to reduce the amount of investment required to purchase agricultural materials, fertilizer, feed, and so on. The most crucial requirement for precision field management is an accurate understanding of the soil conditions which prevail in a given field. Soil, after all, is the most important element in agricultural production.
When light is projected onto the soil, it is absorbed. It is well known that the wavelength and intensity of the absorbed light will vary with the components of the soil and their quantities. Accordingly, the reflected wave will display characteristic optical spectra (i.e., absorbed spectra) depending on the components of the soil.
Heretofore, then, it was found to be possible to analyze the composition of soil by surveying and analyzing its optical spectra.
An example of an optical soil survey device to survey the optical characteristics of a soil in order to investigate soil conditions in a given field is disclosed in U.S. Pat. No. 5,044,756, which is pictured in FIGS. 19 through 21.
FIG. 19 is a cross section of the part of the device which, while mounted on a vehicle, moves the survey surface of the earth to excavate and examine the soil. Excavation and sensing unit 20 is composed of casing 21, which, as the vehicle advances, progressively excavates the soil. Cutting end 23, which turns up soil 22 as the vehicle advances in direction A, is on the front end of unit 20. The lower portion of the soil near the survey surface which is turned up by cutting end 23 is compressed by casing 21 to produce a flat soil survey surface 24.
Inside casing 20, in the portion facing soil survey surface 24, is an opening 26 which creates a chamber 25. In this chamber the characteristics of the soil are surveyed. On the ceiling of chamber 25 are red light-emitting diodes 28, which project light onto soil survey surface 24, and photodiodes 29, which receive the light reflected off the soil. A cable 27 is used for wiring.
With this design, cutting end 23 on the front of casing 21 turns up soil 22 and creates flat survey surface 24, and as this is happening the characteristics of the soil are surveyed at survey surface 24.
As casing 20 advances, some of the soil which constitutes survey surface 24 moves into chamber 25, which eventually fills up with soil. When this happens, it becomes impossible to survey the characteristics of the soil on survey surface 24.
To address this problem, the device disclosed in U.S. Pat. No. 5,044,756 has an opening 32 in the back of chamber 24 through which the soil which has entered the chamber can escape.
Because casing 21 is advancing quite close to the survey surface of the ground, stray light from the survey surface is apt to enter the chamber through this opening. Thus the escape hole for the soil is made as small as possible.
FIG. 20 is a view of the device in FIG. 19 from underneath. The tip 23a of cutting end 23 is formed at an acute angle so that it can easily cut through the soil.
FIG. 21 is a perspective drawing of the device in operation.
As is discussed above, the aforesaid device to survey optical soil characteristics which is disclosed in U.S. Pat. No. 5,044,756 has a cutting end 23 on the front of its casing 21. As this cutting end 23 turns up soil 22 and creates a flat survey surface 24, it treats this survey surface as the object of investigation in order to survey the characteristics of the soil.
The prior art device to survey the optical characteristics of the soil which is described above has the following shortcomings.
(1) As can be seen in FIG. 20, the tip 23a of cutting end 23 on the front of casing 21 is formed as an acute angle so that it can easily turn up soil 22. As is shown in FIG. 19, as cutting end 23 proceeds it turns up a depth of soil which extends from ground level 30 to soil survey surface 24, that is, the depth indicated by H in FIG. 19. And as can also be seen in FIG. 20, the width T of casing 21 is considerable. As a result, cutting end 23 encounters significant resistance from the surrounding soil as it proceeds, removing the soil and digging a furrow of width T and depth H.
(2) Because casing 21 moves along quite close to the survey surface of the ground, stray light is apt to enter sensing chamber 25. To prevent the entry of stray light, opening 32 to evacuate soil from the chamber is kept very small; however, the small size of opening 32 makes it liable to become clogged with particles of the surrounding soil. When this happens, dirt begins to accumulate in chamber 25 and it becomes impossible to survey the characteristics of the soil.
The object of this invention is to provide an optical soil survey device to survey the optical characteristics of a given soil, a soil survey device to survey the soil, a soil survey system and a mobile soil survey vehicle to survey the soil, all of which, survey the optical characteristics of a given soil which would, without experiencing significant resistance from the soil, be able to survey the various components of the soil and/or the optical characteristics of the soil accurately and without being affected by stray light.
To survey the characteristics of a soil (including both optical, electrical characteristics, and other types of characteristics detected by other types of sensors), it is necessary to ascertain the depth of the soil being treated. Thus to survey soil characteristics at a given depth, we must excavate the soil in such a way as to form a survey surface at that depth which we can examine. The space required to operate the sensor which examines the soil must be kept to a minimum, and it should be as close as possible to the aforesaid survey surface. If this is done, not much of the soil above the survey space need be excavated, so less resistance is offered by the soil when it is excavated. The shaft extending upward from the survey surface to the ground which accompanies excavation is kept small, which minimizes the pernicious effect of stray light on an optical survey of the soil characteristics which is experienced when sunlight penetrates the aforesaid survey chamber via this shaft.
However, if a construction tool to create such a subterranean chamber is to be driven with a vehicle which traverses the survey surface, the two will somehow have to be conjoined. It is thus impossible to avoid creating some degree of furrow on the survey surface of the ground. To reduce the quantity of stray light which strikes the sensor, we must refill this furrow with soil so that it does not furnish a route for stray light. The basic concept underlying this invention, then, is to realize a design such that very little of the soil above the survey chamber is turned up, or if it is turned up and a furrow is left, such that the furrow is immediately refilled so as to minimize the pernicious effect of stray light.